The goal of this project is to describe the epidemiology and clinical characteristics of a new group of Chlamydia psittaci agents that have been associated with human respiratory tract infections. The organisms have been isolated only in embryonated eggs, are of low virulence, appear to be separate immunologically from other C. psittaci, and may be spread by human to human transmission without a bird or animal reservoir. In order to facilitate epidemiological and clinical studies, a cell culture system sensitive for isolation of the organisms will be sought through studies of different cell types with chemical (DEAE-dextran, cycloheximide) and physical (temperature of incubation, centrifugation of inoculum) treatments to enhance growth of the organisms. Type- and species-specific monoclonal antibodies against the new C. psittaci organisms will be produced. These antibodies when conjugated to fluorescein will enhance the demonstration of inclusions in cell culture, and will allow demonstration of elementary bodies in smears of clinical specimens. Patients for study will be provided by the clinics and hospitals affiliated with the University of Washington including the student health clinic. Following improvements in diagnostic techniques, family studies will be undertaken. A clinic patient will be the index case to identify families for observation. The frequency of infection in family members, the range of clinical severity, the incubation period, and the potential relationship to a bird/animal reservoir will be studied. Studies in a defined population group will be performed to determine the age, sex, and seasonal incidence of infection. Since C. psittaci infection can be successfully treated with certain antibodies, recognition and specific diagnosis has important therapeutic consequences. Studies on the biology of these new organisms will include their ability to infect, cause illness and death in mice following IV, IP, and IN inoculation. A separate but related task is the development of an immunoclassification scheme for C psittaci. The two techniques employed for successful classification of C. trachomatis will be utilized: the two way micro-immunofluorescence test and type- and subspecies-specific monoclonal antibodies. Classification of the C. psittaci species will aid in determining the relationship of the new group of strains to other members of the species.